Hardwood Log Grades for Standard Lumber

Transcription

1 U. S. FOREST SERVICE RESEARCH PAPER FPL 63 JUNE 1966 U. S. DEPARTMENT OF AGRICULTURE FOREST SERVICE FOREST PRODUCTS LABORATORY MADISON, WISCONSIN Hardwood Log Grades for Standard Lumber

2 ABSTRACT The official U.S. Forest Service Hardwood Log Grades for Standard Lumber are described and tables of expected yields of standard factory grade lumber are presented by species, log grade, and log diameter. With this information, foresters, timber sellers, and timber buyers can separate, from woods-run hardwood logs, those logs suitable for manufacture into standard factory grade lumber. Furthermore, the logs can be ranked into categories of high, medium, and low value and lumber grade yields. The yield tables provide the information to estimate the lumber grade yields to be expected from the graded logs. This report supersedes the previous Forest Products Laboratory report on hardwood log grading (No. 1737). The Forest Products Laboratory of the Forest Service, U.S. Department of Agriculture, is maintained at Madison, Wis., in cooperation with the University of Wisconsin.

3 Hardwood Log Grades for Standard Lumber C. L. VAUGHAN A. C. WOLLIN K. A. McDONALD Forest Products Technologists E. H. BULGRIN U. S. DEPARTMENT OF AGRICULTURE FOREST SERVICE F OREST P RODUCTS L ABORATORY Historically, log quality has been evaluated by log grading systems based on judgment and experience. The hardwood log grades for standard lumber, as developed by the Forest Products Laboratory, are based on an analysis of the relationship between log characteristics and end product yield. This system enables foresters, timber sellers, and timber buyers to separate, from woods-run hardwood logs, those logs suitable for manufacture into factory grade lumber and to rank the logs into categories of high-, medium-, and lowquality yields. The yield tables provide the information necessary for estimating the value and volumes of the standard factory lumber grades to be extended from the graded logs. This system for grading hardwood logs was first proposed by the Forest Products Laboratory in 1949 in Laboratory Report In 1952, the proposed grades were adopted as the official hardwood log grades for the U.S. Forest Service. Since the first publication of the grading system, the grade specifications and their application have remained unchanged. This report updates Report No. 1737, adds a limited amount of new yield data, and includes some adjustments in the original yield data. DESCRIPTION OF METHODS OF FIELD STUDY AND ANALYSIS Approximately 11,000 logs as sawed at 28 sawmills in the northern, central, and southern hardwood regions are included in the studies covered by this report. Each study log was diagramed, providing as accurate a record as possible of the exterior and ends of the log. Logs were then sawed and the yield per log, in board feet of green lumber, was tallied by board grade and thickness. Green lumber yield was reduced by 5 percent to allow for shrinkage during seasoning. No allowance was made for degrade that might occur during seasoning. These basic data were 1 Other members of the Forest Service have given valuable assistance. 2 Published by the U.S. Forest Products Laboratory as Hardwood Log Grades for Standard Lumber--Proposals and Results, FPL Report 1737, March A pocket edition, D1737-A, was also issued by the Laboratory in I949 as Hardwood Log Grades for Standard Lumber and How to Apply Them.

4 then used to develop log grade specifications and yield tables. The data were first sorted into groups of logs having similar yields by grade. Each group of data from logs with similar grade yields was then sorted into groups of logs having similar external characteristics. These data were then analyzed and the basic specifications for log grades were determined. HARDWOOD LOG GRADES FOR STANDARD LUMBER Three grades are considered sufficient for commercial evaluation of factory lumber logs. Analysis of the basic data made it possible to establish specifications so that each log grade attracts to itself logs having similar standard lumber grade yields and values. Each of the three log grades--high, medium, and low--has corresponding lumber grade yields with high, medium, and low average values. The log grade specifications are correlated closely with the specifications for standard hardwood lumber grades. A board is graded on the basis of clear-faced or sound cuttings of a minimum size to comprise a certain fraction of the area of the board; logs are similarly graded on the clear cuttings of a definite minimum size comprising a specified fraction of the area of one-quarter of the circumference of the log. The log grade specifications are listed in figure 1. HOW TO USE THE LOG GRADES The grading of logs is not as difficult as it may first appear. The basic requirements are a knowledge of surface indicators of interior defect, and a knowledge of the log grade specifications. Knowledge of surface indicators can be gained by a careful study of Agriculture Handbook No. 244, Grade Defects in Hardwood Timber and Logs, 3 and observation in a sawmill. Knowledge of the log grade specifications and their interpretation can be gained by studying A Guide to Hardwood Log Grading and by experience. With experience, log grade can be determined in most cases in the process of scaling the log. Even in the logs where grade is not immediately apparent, it is seldom necessary to lay out the actual cuttings. Usually measurements to see whether the cuttings conform to the minimum size will be enough to determine the grade. Faces After taking into account the size and soundness of the log, the first step in grading is to visually divide the surface of the log (full length) into four equal faces, so oriented as to give the greatest possible number of good faces. The influence of a given defect should be confined to one grading face wherever possible instead of permitting it to extend over two faces. Clear Cuttings The next step is to establish the grade of the best three faces on the basis of the clear cutting requirements. Only when two of these faces grade higher than the third is it necessary to examine the fourth face to be sure that the best faces have been selected. The grade of the log is that of the lowest of the faces chosen as the three grading faces. The clear cuttings are taken as the portions of the length of the face that lie between defects or between the ends of the logs and defects and extend over the full width of the face. Knots, overgrown knots, grub holes, etc., either projecting or recessed, are excluded from clear cuttings. Sound end defects, such as medium-to-heavy mineral stain in hard maple and yellow-poplar and slight dote in yellow birch on the small end of the log, shall not exceed one-half the log diameter for Grade 1 logs and for Grade 2 logs under 16 inches, and not exceed three-fifths the 3 Lockard, C. R., Putnam, J. A., and Carpenter, R. D. Grade defects in hardwood timber and logs. U.S. Dept. Agr., Agr. Handb. 244, 39 pp Northeastern Forest Experiment Station. A guide to hardwood log grading. U.S. Forest Serv., Northeastern Forest Exp. Sta., Upper Darby, Pa. Revised 1965.

5 Figure 1.--Forest Service standard specifications for hardwood factory lumber logs. Grading Factors Log Grades FI F2 F3 Position in tree Butts Butts & Butts & uppers Butts & only uppers uppers Diameter, scaling, inches l l ll l Length without trim, feet I 0+ l l 0-l l l Clear cuttings 3 on each 3 best faces Length, min., feet Number, maximum Fraction of log length required in clear cutting No Iimit 5/6 5/6 5/6 2/3 3/4 2/3 2/3 l/2 For logs with less Sweep and than l/4 of end in crook sound defects allowance (maximum) in percent For logs with more gross than l/4 of end in volume sound defects l 5% l 0% 30% 50% 20% 35% Total scaling deduction including sweep and crook 30% 6 50% 50% End defects: See instructions page 4. l Ash and basswood butts can be l2 inches if otherwise meeting requirements for small No. l s. 2 Ten-inch logs of all species can be No. 2 i f otherwise meeting requirements for small No. l s 3 A clear cutting is a portion of a face free of defects, 4 See table 46. extending the width of the face. 5 Otherwise No.l logs with 4l-60% deductions can be No Otherwise No.2 logs with 5l-60% deductions can be No. 3. Face 4 Face l Clear cutting Clear cutting Clear cutting Clear cutting Face 3 Face 2

6 log diameter on Grade 2 logs 16 inches and larger. Excess will lower the log one grade. When the defect is not concentrated in one spot, its extent is taken as the sum of the individual occurrences. Slight stain is not a defect. Full-length unsound end defect outside the heart zone (taken as one-fifth of the diameter from the pith), when extending more than one-half the distance between the heart zone and the bark, prevents taking clear cuttings on the face surface overlying it. When it extends less than the full log length, cuttings can be taken over a third of its estimated length from the end tapering out. End defects, such as bird peck, worm holes, spot wormhole stain, mineral spots or streaks, and such unsound defects as grub holes and bark pockets are considered when outside the heart zone, the heart zone being taken as extending one-fifth the diameter of the log from the pith. When these defects affect one-half the radial distance between the heart zone and the bark under three faces of the log at one end, or two faces at both ends, a log of Grade 1 or 2 shall be dropped one grade. When there is less than 3 inches either between the heart zone and the defect, or between defects, the portion will be included with the defect. For seams, frost cracks, and fire or other scars whose depth exceeds one-fifth the diameter but not extending the full length of the log, clear cuttings can be taken over one-third of its length from the end tapering out. Bird pecks are considered defects in cuttings of Grade 1 and Grade 2 logs when the area contains more than four bird pecks per square foot. Also when the depth of the bird peck on the end of the log is less than one-tenth of the log diameter, it is not considered a defect. Sweep, Crook, and Cull Deductions Logs that involve deductions in scale in excess of percentages allowed for each grade are dropped one grade. All deductions that are made by enclosing the defect in a rectangle are computed according to the National Forest Scaling Handbook? by multiplying width, height, and length of defect together and dividing by 15. The maximum percentage deduction for this type of cull as provided for in log grade specifications will apply to Scribner Decimal C, Doyle, or International rules. However, the percentage deduction arrived at when Doyle or International scale is used in grading should be multiplied by the following factors to give the approximate percentage deduction for grading: International Rule (Inches) (Factor) Logs 8 to Logs 15 to Logs 20 to Logs 37 and up..... None (Inches) Doyle Rule (Factor) Logs 8 to Logs 12 to Logs 14 to Logs 21 to None Logs 32 to For sweep, the rule-of-thumb given in the Handbook is replaced by the provision that the percentage deduction is taken as the maximum sweep minus 2, divided by log diameter. Measurement of Log Diameter and Length Average diameter inside the bark on the small end of log is used in scaling and grading. The length for figuring the necessary clear cuttings is dropped to the full foot, but the cuttings are allowed to include the overlength. LUMBER GRADE YIELDS Lumber grade yields and lumber thickness by species, log grade, and diameter are given in 5 U.S. Forest Service. N a t i onal Forest scaling handbook. U.S. Dept. Agr., Forest Serv. Handb

7 tables 1 through 45. The information listed here, together with current lumber prices, will enable interested parties to calculate an estimated value for a group of logs. The clear cutting requirements are converted from fractions to actual lengths by log length in table 46. Slight bark distortion, consisting of a simple break across the normal bark pattern--not a defect. Medium bark distortion consisting of compound breaks across and along the normal bark pattern--a defect in logs of al I diameters.

8 Bark distortion that clearly is an overgrown knot--a defect in logs of all diameters. Adventitious twig growth 3/8 inch or less in diameter is a defect in logs under I4 inches d.i.b. On logs I4 inches and larger, only every other one is considered a defect. In the nondense hardwood species it is not considered a defect in grade 3 logs. Grub holes and grub-caused overgrowths: On logs 8-15 inches--each is a full defect. On logs inches--disregard every 6th one. Logs inches--disregard every 5th one. On logs inches--disregard every 4th one. On logs 28 inches or more--disregard every 3rd one.

9 A bump is taken as any bark-covered protuberance with gradual to abrupt sloping sides, the cause of which is not clearly evident. Bumps are not considered defects in logs: Under l4 inches d. i. b. when the length of the bump is l6 or more times its height. Nor in l4-inch logs and over d. i. b. when the length of the bump is I2 or more times its height. Measurement of clear cuttings may extend into both ends of bumps by: l/4 when length is 6 or more times the height. l/8 when length is 3, but less than 6, times the height. Key to Symbols for Tables 1-45 No. of logs = actual number of logs sampled. DIB (inches) = scaling diameter at the small end of the log. Scale Int. 1/4 Inch = international 1/4-inch log rule. Gross (bd. ft.) = gross scale before deductions. Net (bd. ft.) = net scale after deductions. Overrun (pct.) = lumber tally minus net scale divided by net scale. Scrib. Dec. C = Scribner Decimal C log rule. Gross (bd. ft.) = gross scale before deductions. Net (bd. ft.) = net scale after deductions. Overrun (pct.) = lumber tally minus net scale divided by net scale. Lumber tally (bd. ft.) = volume of green lumber tally reduced by 5 percent. NHLA Lumber Grade Yields (Actual) = actual lumber grade yields in percent by National Hardwood Lumber Assoc. lumber grades. FAS = Sel = Saps = 1C = 2C = 2A = 2B = SW = 3A = 3B = Tmbrs. Firsts and seconds Select Saps, yellow-poplar only No. 1 Common No. 2 Common No. 2A Common, yellow-poplar only No. 2B Common, yellow-poplar only Sound wormy No. 3A Common No. 3B Common & SSE = Ties, timbers, and sound square edges Lumber thickness (inches) - shown by quarters of inches. 4/4 and below = all lumber 1 inch thick and thinner. 8/4 and above = all lumber 2 inches thick and thicker.

10 Table I.--Basswood, Log Grade l--lumber grade yield by diameter Distribution by thickness of Log Grade I yields FPL 63 8

11 Table 2.--Basswood, Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields

12 Table 3.--Basswood, Log Grade 3--Lumber grade yield by diameter Distribution by thickness of Log Grade 3 yields FPL 63 10

13 Table 4.--Yellow Birch, Log Grade l--lumber grade yield by diameter Distribution by thickness of Log Grade I yields 11

14 Table 5.--Yellow Birch, Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields FPL 63 12

15 Table 6.--Yellow Birch, Log Grade 3--Lumber grade yield by diameter Distribution by thickness of Log Grade 3 yields 13

16 Table 7.--Sap Gum, Log Grade l --Lumber grade yield by diameter Distribution by thickness of Log Grade I yields FPL 63 14

17 Table 8.--Sap Gum, Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields 15

18 Table 9.--Sap Gum, Log Grade 3--Lumber grade yield by diameter Distribution by thickness of Log Grade 3 yields FPL 63 16

19 Table l 0.--Hard MapIe, Log Grade I--Lumber grade yield by diameter Distribution by thickness of Log Grade I yields 17

20 Table I l.--hard Maple, Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields FPL 63 18

21 Table I2.--Hard Maple, Log Grade 3--Grade yield by diameter Distribution by thickness of Log Grade 3 yields 19

22 Table l 3.--Black Oak, Log Grade I --Lumber grade yield by diameter Distribution by thickness of Log Grade I yields FPL 63 20

23 Table l 4.--Black Oak, Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields 21

24 Table l 5.--Black Oak, Log Grade 3--Lumber grade yield by diameter Distribution by thickness of Log Grade 3 yields FPL 63 22

25 * Table l6.--chestnut Oak (WHAD), Log Grade I --Lumber grade yield by diameter Distribution by thickness of Log Grade I yields *Lumber graded WHAD--worm holes a defect. 23

26 Table l 7.--Chestnut Oak (WHAD), Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields FPL 63 24

27 Table l Chestnut Oak (WHAD), Log Grade 3--Lumber grade yield by diameter Distribution by thickness of Log Grade 3 yields 25

28 * Table l 9.--Chestnut Oak (WHND), Log Grade l --Lumber grade yield by diameter Distribution by thickness of Log Grade I yields *Lumber graded WHND--worm holes no defect. FPL 63 26

29 Table 20.--Chestnut Oak (WHND), Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields 27

30 Table 2 l.--chestnut Oak (WHND), Log Grade 3--Lumber grade yield by diameter Distribution by thickness of Log Grade 3 yields FPL 63 28

31 Table 22.--Red Oak (Lowland), Log Grade I --Lumber grade yield by diameter Distribution by thickness of Log Grade I yields 29

32 Table 23.--Red Oak (Lowland), Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields FPL 63 30

33 Table 24.--Red Oak (Lowland), Log Grade 3--Lumber grade yield by diameter Distribution by thickness of Log Grade 3 yields 31

34 Table 25.--Red Oak (Upland), Log Grade I --Lumber grade yield by diameter Distribution by thickness of Log Grade I yields FPL 63 32

35 Table 26.--Red Oak (Upland), Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields 33

36 Table 27.--Red Oak (Upland), Log Grade 3--Lumber grade yield by diameter Distribution by thickness of Log Grade 3 yields FPL 63 34

37 Table 28.--White Oak (Lowland), Log Grade I --Lumber grade yield by diameter Distribution by thickness of Log Grade I yields 35

38 Table 29.--White Oak (Lowland), Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields FPL 63 36

39 Table 30.--White Oak (Lowland), Log Grade 3--Lumber grade yield by diameter Distribution by thickness of Log Grade 3 yields 37

40 Table 3 I.--White Oak (Upland), Log Grade I --Lumber grade yield by diameter Distribution by thickness of Log Grade I yields FPL 63 38

41 Table 32.--White Oak (Upland), Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields 39

42 Table 33.--White Oak (Upland), Log Grade 3--Lumber grade yield by diameter Distribution by thickness of Log Grade 3 yields FPL 63 40

43 Table 34.--Yellow-Poplar, Log Grade l --Lumber grade yield by diameter Distribution by thickness of Log Grade I yields 41

44 Table 35.--Yellow-Poplar, Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields FPL 63 42

45 Table 36.--Yellow-Poplar, Log Grade 3--Lumber grade yield by diameter Distribution by thickness of Log Grade 3 yields 43

46 Table 37.--Beech, Log Grade I --Lumber grade yield by diameter Distribution by thickness of Log Grade I yields FPL 63 44

47 Table 38.--Beech, Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields 45

48 Table 39.--Beech, Log Grade 3--Lumber grade yield by diameter Distribution by thickness of Log Grade 3 yields FPL 63 46

49 Table 40.--Cottonwood, Log Grade l--lumber grade yield by diameter Distribution by thickness of Log Grade l yields 47

50 T a b l e 4 l.--cottonwood, Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields FPL 63 48

51 Table 42.--Cottonwood, Log Grade 3--Lumber grade yield by diameter Distribution by thickness of Log Grade 3 yields 49

52 Table 43.--Elm, Log Grade I --Lumber grade yield by diameter Distribution by thickness of Log Grade I yields FPL 63 50

53 Table 44.--Elm, Log Grade 2--Lumber grade yield by diameter Distribution by thickness of Log Grade 2 yields 51

54 Table 45.--Elm Log Grade 3--Lumber grade yield by diameter Distribution by thickness of Log Grade 3 yields Table 46.--Clear cutting requirements FPL

55 Tables Showing Lumber Yield by Grade and Diameter Table No Species Log Page on Table Grade Which Shown No. Species Log Page on Grade Which Shown 1 Basswood 2 Basswood 3 Basswood Red Oak (Upland) 9 26 Red Oak (Upland) Red Oak (Upland) Yellow Birch 5 Yellow Birch 6 Yellow Birch White Oak (Lowland) White Oak (Lowland) White Oak (Lowland) Sap Gum 8 Sap Gum 9 Sap Gum White Oak (Upland) White Oak (Upland) White Oak (Upland) Hard Maple 11 Hard Maple 12 Hard Maple Yellow-Poplar Yellow-Poplar Yellow-Poplar Black Oak 14 Black Oak 15 Black Oak Beech Beech Beech Chestnut Oak (WHAD) 17 Chestnut Oak (WHAD) 18 Chestnut Oak (WHAD) Cottonwood Cottonwood Cottonwood Chestnut Oak (WHND) 20 Chestnut Oak (WHND) 21 Chestnut Oak (WHND) Elm Elm Elm Red Oak (Lowland) 23 Red Oak (Lowland) 24 Red Oak (Lowland)

56 UNITED STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE FOREST PRODUCTS LABORATORY MADISON. WISCONSIN